Conventionally, door suspension devices that support a door provided in a structure and driven to be opened and closed by an open-close drive mechanism, in a state in which the door is suspended to the structure so as to be slidably moved, and that is connected to the open-close drive mechanism are known (for example, see Patent Document 1). As a door suspension device used in a railroad vehicle serving as a structure, Patent Document 1 discloses a door suspension device including a rail member including an upper rail and a lower rail, and a door roller device including door rollers that run on the rail member. Also, in Patent Document 1, a door suspended to the door suspension device is driven to be opened and closed by an open-close drive mechanism connected to the door suspension device, and the door is supported in a state of being suspended to the structure, which is a side wall of the railroad vehicle, so as to be slidably moved.
Further, the door roller device of the aforementioned door suspension device is provided with a supporting member disposed along the lengthwise direction of the rail member, and this supporting member is provided with a first door roller capable of running on the lower rail and a second door roller capable of running on the upper rail. The second door roller is provided at one end of the supporting member, and a suspender capable of suspending the door is provided on the other end of the supporting member. Accordingly, the self-weight of the door is exerted on the suspender, the second door roller comes into contact with the upper rail with the first door roller, which runs on the lower rail, serving as a fulcrum, and the door is thereby supported. Accordingly, it is possible to provide a door suspension device that can prevent the derailing of doors from a rail member, enable smooth and safe opening and closing of doors, and achieve a reduction in manufacturing and installation costs.